Three weeks after head trauma, a 30-year-old woman reports a continuous clear, salty-tasting unilateral nasal discharge that increases on bending forward. Fluid collected from the nose is sent for analysis. Which finding confirms the fluid to be cerebrospinal fluid?

• A High sodium and low potassium content
• B Glucose concentration above 100 mg/dL
• C Presence of beta-2 transferrin ✓
• D Presence of beta-trace protein alone on dipstick testing

Explanation

Beta-2 transferrin, the desialated isoform found almost exclusively in cerebrospinal fluid, aqueous humour and perilymph, is the gold standard biochemical marker for confirming a CSF leak. Nasal secretions and tears contain beta-1 transferrin but not the beta-2 isoform. Glucose testing produces false positives because normal nasal secretions contain glucose, and beta-trace protein can be elevated in other body fluids, so it is less specific when used alone. Confirmation guides timing of endoscopic repair.

Reference: Cummings Otolaryngology Head and Neck Surgery, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.